Flocked materials for use in automotive sealing systems are well known. Most often, these flocked materials are made of a vulcanized rubber component to which a primer and an adhesive have been applied. A flock material is then added that adheres to the adhesive. Many problems exist with the preparation of these materials, including environmental concerns related to the solvent-based primers and adhesives that are usually employed. Further, the application of the primers and adhesives must usually be done in excess in order to obtain sufficient coverage of the vulcanized rubber substrate, further increasing the cost of these systems.
Changes to the substrate materials have led to changes in the materials needed to create flocked substrates for use in automotive sealing systems. In particular, thermoplastic elastomers (“TPEs”) and thermoplastic vulcanizates (“TPVs”) are prime contenders to replace vulcanized rubbers in these sealing systems. The reprocessability and superior physical characteristics of the TPEs and TPVs make them more desirable for use in the sealing systems. However, many of these same characteristics make the TPEs and TPVs less desirable for use with the prior adhesion systems for creating flocked materials. In particular, when a polypropylene is used as the thermoplastic phase of a TPV, the non-polar polypropylene does not provide a surface readily used for the adherence of mostly polar flock materials. New solvent-based adhesives have been used, but retain the undesirable cost and environmental impacts of the prior generation of the adhesives. Certain water-based adhesives have been used in an attempt to avoid the environmental impacts of solvent-based ones, but these often require the use of a primer to first prepare the polypropylene surface before the adhesive will sufficiently adhere to it. The use of primer increases costs and also has undesirable environmental impacts. Additionally, the water-based adhesives currently available often do not provide sufficient performance to keep the flock adhered to TPV substrate materials over the thousands of operation cycles to which an automotive sealing system such as a glass run channel is subjected.
There then exists a need for a non-solvent based adhesive system which will readily allow the flocking of non-polar substrates such as polypropylene or polypropylene-based TPVs with polar flocks (such as polyester or nylon) while maintaining good adherence to the substrate over an extended time period and under demanding conditions of exposure to the elements and large numbers of operation cycles.
The present invention provides a composite structure made up of a second component (a grafted propylene-based elastomer in one embodiment) and a third flock component in the form of a ribbon or tape that provides excellent compatibility with non-polar substrates, particularly polypropylene-based TPVs. In another aspect, a substrate is used that may be pre-formed into a shape, including that of a desirable end use product, and the second component and a flock components are adhered to it. In yet other aspects, the present invention provides processes for producing these composite structures, useful articles formed from them and methods for producing the same.